I'm basically trying to work out how to take a slice of an image, say a screenshot of an iPhone home screen, slice out the first icon and compare it to a set array of images in a library. Any help on where to start?
I'm no iPhone programmer, but I might be able to suggest a few things:
The SURF feature detection implemented in OpenCV should help you with this
There is a nice article on using OpenCV in Objective-C code.
A quick & dirty way might be to use the difference blend mode which should return the difference between the 1st image(top) and the 2nd image(bottom). If there is no difference the result will be completely black. So, the more black pixels in the difference result, potentially, the more similarities between the compared images.
I'm not an iOS developer, so I don't know if there is an image library that ships with sdk or if there's a free/opensource library for basic image processing. Still this should be trivial to implement:
e.g.
- (int)difference((int)topPixel,(int)bottomPixel)
{
return abs(topPixel-bottomPixel);
}
Note: Syntax might not be correct :)
HTH
This may not help you with taking a screenshot of the iOS home screen... But these articles show how to take snapshots from within a UIKit application:
https://developer.apple.com/library/prerelease/ios/#qa/qa1703/_index.html
https://developer.apple.com/library/prerelease/ios/#qa/qa1714/_index.html
Perhaps you would instruct the user to press home-power (buttons) to take a snapshot and store in the photo roll, then load that screenshot into an app to process the screenshot.
Hope this helps!
Related
I am using AVFoundation to take pictures instead of UIImagePicker due to how customizable the user interface presented to the user can be. When using it the aspect ratio that the picture is saved as is the same as the iPhone's video feed. What I want to happen is to have the pictures saved in the same aspect ratio as normal pictures are.
The way that I am currently approaching this is to overlay a black bar in the excess preview display and then just crop the photo after saving it as an image.
However, this feels very crude. I assume that it is a common thing to use the AVFoundation as a way of taking photos and so I assume I must be missing something!
I have used this example code. And I have read through the AVFoundation documentation but can only assume that I am missing a function. I have also read through similar questions to this which describe the process by which I might go about cropping images, but that isn't really my concern.
On the other hand, if there is no standard way to do this, please do let me know so that I can stop worrying that I am approaching it in a convoluted way.
Also, I am using Objective-C so if answers contain code, please could you use the same language?
I'm building an iphone photo app. I don't know how to achieve this kind of effect on an image:
When the user drags a finger across the arrow, I want the image to be distorted accordingly. How can I achieve this? Is there any framework that makes this process simple?
Thank you.
No clue about iOS, but the look reminds me of a thin-plate spline warp. It's quite easy to implement in OpenGL, a quick Google search for example code returns plenty of hits.
From the sound of it I think your looking for the CoreImage framework. Look into the various distortion effects...in particular CIBumpDistortionLinear.
I don't have any code so check out this tutorial and read up on CoreImage.
I'm investigating if it's possible to implement the same functionalities of ZBar library with iOS 7 api.
Everything was good so far thanks to this tutorial.
However, I now want to have a green box shown on the screen whenever the camera detects a QRCode. The green box is supposed to wrap around the QRCode.
From the delegate of AVCaptureMetadataOutput, I can grab AVMetadataObject but the bounds getting from this object is always very small which is not correct, given the fact that my QRCode is very big on the screen.
Anyone has any ideas on how to achieve the green focusing box?
P/S: I came across the documentation and couldn't understand this line "If the metadata originates from video, bounds
may be expressed as scalar values from 0. - 1.". This is for the bounds property of AVMetadataObject
You can look at this tutorial for qrCode scanning using iOS 7.
I had to do the same thing in my scanner app. Here is a link that I found very useful and pretty much answered all my questions.
He goes step by step from setting up the scanner to adding the bounding box.
I'm following this guide: http://www.aishack.in/2010/08/sudoku-grabber-with-opencv/2/
and modifying to iOS 5.0.
I managed to find the largest contour (the sudoku "board"), however, it only locates the surrounding square, without the lines inside, as in the tutorial. can this be easily solved?
I'll try and find a way around it, but still would like to know. thanks!
I assume that you are using the camera right now. Try to load the image what is used in the tutorial and check if your implementation works on that image. Then you can continue with nice sudoku images from the web. You may also change the camera angle and distance from the sudoku when taking pictures to get a better, clearer view.
Actually I am adding Image Processing Feature in my iPhone Application It should do Brightness, Contrast, Sharpen, Exposure....
But i am not able to Find any article/Tutorial on the Internet. Will you please help me to find any tutorial or tell me how can i implement the iPhone View Based Application.
I have found 1 link http://www.iphonedevsdk.com/forum/iphone-sdk-development/10094-adjust-image-brightness-contrast-fly.html its worked also for Brightness but its not working on iPad.
So Suggest something that i can start with my Image Processing Logic.
Thanks
Rick Jackson
I personally like the approach in the GLImageProcessing project from Apple's sample code. Check it out.
There are a few libraries that support image processing in Quartz. There are even a few categories on UIImage to do some basic stuff.
The following are a few examples:
https://github.com/esilverberg/ios-image-filters
https://github.com/cmkilger/CKImageAdditions
http://code.google.com/p/simple-iphone-image-processing/
But as said before by #Felz those libraries are slow because they use the quartz codebase, which isn't that fast (for example: changing the saturation of an image with a resolution of 1024x1024 might take up to 4 to 8 seconds, depending on which device your using).
If your project is iOS 5 or higher then you should definitely consider using CoreImage
You can try GPUImage framework created by Brad Larson. It includes awesome image filters and also easy to use.